WO2020234219A1

WO2020234219A1 - Sensor and device for presence detection

Info

Publication number: WO2020234219A1
Application number: PCT/EP2020/063770
Authority: WO
Inventors: Olivier Elie; Gabriel Spick
Original assignee: Continental Automotive Gmbh
Priority date: 2019-05-22
Filing date: 2020-05-18
Publication date: 2020-11-26
Also published as: FR3096389B1; US20220235589A1; US11933084B2; CN113892233A; FR3096389A1

Abstract

The invention relates to a presence detection sensor (1) for unlocking an opening panel of a motor vehicle, said sensor (1) comprising a microcontroller (10), using an analog-digital converter (ADC) and comprising a first input (E1), a second input (E2) constituting the voltage reference of the analog-digital converter (ADC), a third input (E3), for supplying voltage to the microcontroller (10) and a plurality of input-outputs (S1, S2, S3), and a capacitive voltage divider (20) connected to at least one of the input-outputs (S1, S2, S3) of the plurality of input-outputs (S1, S2, S3). The sensor (1) comprises a resistive module (Rin) connected between the first input (E1) and the second input (E2) of the microcontroller (10) and a capacitive module (Cin), connected between the second input (E2) of the microcontroller (10) and a ground (M).

Description

DESCRIPTION

TITLE: Sensor and presence detection device

[Technical area]

[0001] The present invention relates to the automotive field and more particularly relates to the unlocking of an access to a motor vehicle. The invention relates to a sensor and a method for detecting the presence of a user near a vehicle as well as a vehicle comprising such a sensor.

[0002] The invention aims in particular to improve the sensitivity of existing CVD and DCVD type sensors.

[State of the prior art]

[0003] In a motor vehicle, it is known practice to use an access unlocking system comprising a sensor for detecting the presence of a user. Such a sensor is in a known manner in the form of a capacitive proximity sensor making it possible to detect for example the presence of a user's hand on the handle of a door in order to unlock it or else to detect the passage. one foot of the user under the trunk of the vehicle in order to unlock it. In particular, when the user moves his hand from a first position, for example away from a door handle, to a second position, on said handle, the sensor detects this presence, which causes the door to unlock.

[0004] In a known solution, called CVD (Capacitive Voltage Divider in English or capacitive voltage divider), the detection sensor comprises a printed circuit comprising a so-called "detection" capacitor forming a first electrode and a so-called "storage capacitor" », Connected via switches to a voltage generator and to a microcontroller implementing an analog-to-digital converter making it possible to quantify the electric charge stored in the storage capacity.

[0005] In the absence of a user near the sensor, the storage capacity is charged with a nominal load defining a nominal storage voltage. When the user's hand is near the electrode, the user behaves like a second electrode, connected to Earth, which increases the capacitance value of the sensing capacitor beyond its capacitance value. nominal measured in the absence of user.

[0006] In order to detect the presence of a user, the sensor first of all comprises an acquisition phase which allows the storage capacity to be loaded, the latter being previously unloaded. This acquisition phase firstly comprises the charging of the detection capacitor by the voltage generator followed in a second step by the transfer by current conduction of the charge stored in the detection capacitor to the storage capacitor. The voltage at the terminals of the storage capacitor is then measured in a second so-called measurement phase.

[0007] When the storage capacity is charged without a user having come near the sensor, its charge at the end of the acquisition phase corresponds to its nominal charge value and the storage voltage to its terminals therefore corresponds to a nominal storage voltage. On the other hand, when a user is present near the sensor during the acquisition phase, the capacitance value of the detection capacitor increases due to the presence of the user so that the voltage defined at the terminals of the storage capacity at the end of the acquisition phase is greater than the voltage defined by the nominal load measured in the absence of human presence near the sensor. In this case, the voltage at the terminals of the storage capacitor is equal to a detection voltage which is greater than the nominal storage voltage. Once a user has been detected, the microcontroller sends a detection signal to an electronic computer in the vehicle so that it authenticates the user and unlocks the opening (s) if necessary.

[0008] This CVD-type solution allows rapid measurements and detection of the presence of a user. However, it was found that this operation could generate significant electromagnetic disturbances, in particular low-frequency noise, which could disturb other electronic devices of the vehicle. In addition, the sensitivity of such a sensor can be relatively low, which implies a short detection distance.

[0009] Also, in order to at least partially remedy these drawbacks, it is known to use an alternative solution, called DCVD (Differential Capacitive Voltage Divider). In this solution, the detection sensor is identical to that of the CVD solution but includes a different arrangement of switches in order to make it operate differently. This solution consists first of all in carrying out a first acquisition phase, identical to the acquisition phase of the CVD solution, followed by a second acquisition phase consisting in charging the storage capacity from the voltage delivered by the voltage generator and then to discharge the storage capacity into the detection capacity. When the detection capacitor is charged without a user having come near the sensor, the charge of the detection capacitor at the end of the second acquisition phase corresponds to its nominal charge value and the storage voltage at the terminals of the storage capacitor therefore corresponds to a nominal storage voltage. On the other hand, when a user is present near the sensor during the second acquisition phase, the capacitance value of the detection capacitor increases so that the voltage defined at its terminals at the end of the acquisition phase or lower than the voltage defined by the nominal load measured in the absence of human presence near the sensor.

Once the first acquisition phase and the second acquisition phase have been completed, the microcontroller analyzes the difference between the voltage measured during the first acquisition phase, which increases in the presence of a user near the sensor, and the voltage measured during the second acquisition phase, which decreases in the presence of a user near the sensor. The sequence of these two acquisition phases can significantly increase the duration of the measurements and thus make the detection of the presence of a user near the sensor significantly time-consuming, which presents a significant drawback.

DCVD capacitive measurement uses the principle of capacitive divider bridge: the voltage measured at the terminals of the electrode capacitor is linked to its capacitance itself. In order to have a satisfactory sensitivity, it is necessary that the measurement of this voltage, carried out by the analog-digital converter of the microcontroller, has the best possible resolution, that is to say that a variation of one digit in the value digital measured by the analog-to-digital converter corresponds to the smallest possible voltage variation.

The voltage corresponding to a digit is given by the following formula:

[0014] [Math. 1]

AV = ¾ ^ _ ^c , where ADCbit corresponds to the number of bits of the analog-to-digital converter and V _re t_ADc corresponds to the reference voltage of the analog-to-digital converter.

The reduction in sensitivity can therefore be done either by reducing V _re t_ADc, or by increasing ADCbit.

[0017] It is known in the prior art to adjust the reference voltage V _re t_ADc using a resistive divider bridge at the input of the microcontroller in order to adapt the reference voltage V _ref-AD c from the analog-to-digital converter closest to the sensor's operating zone. This reference voltage V _re t_ADc must be adjusted so that it is always greater than the voltage to be measured, otherwise the measurement will be saturated.

However, it turns out that with such a circuit, the DCVD capacitive signal is sometimes too weak to have satisfactory sensitivity. In addition, the adjustment of the reference voltage V _re t_ADc by a resistive divider bridge does not make it possible to maximize the resolution of the analog-to-digital converter because, to avoid saturation in worst-case situations, it is then necessary to overestimate the reference voltage V _re t_ADc.

[0019] There is therefore a need for a simple, reliable and efficient solution making it possible to remedy at least in part these drawbacks and in particular aimed at improving the sensitivity of existing detection sensors.

[Disclosure of the invention]

[0020] To this end, the invention firstly relates to a presence detection sensor for unlocking a motor vehicle opening, said sensor comprising:

a microcontroller comprising an analog-to-digital converter, a first input-output port, a second input-output port, constituting the voltage reference of said analog-to-digital converter, a third input-output port, power supply of the microcontroller, a fourth input-output port and a fifth input-output port, called "connection",

a capacitive voltage divider, connected to said connection input-output ports and comprising at least one detection capacitor and at least one storage capacitor, the sensor being remarkable in that it comprises a resistive module connected between the first input-output port and the second input-output port of the microcontroller and a capacitive module, connected between the second input-output port of the microcontroller and a ground, and in that the microcontroller is configured to connect so internal the first input-output port and the third input-output port for a so-called predetermined “charging” time of the capacitive module in order to dynamically establish the reference voltage of the analog-to-digital converter. The term “input-output” is understood to mean an input or an output or else both an input and an output, if applicable.

The microcontroller can thus control the load of the capacitive module through the resistive module in order to dynamically set the reference voltage of the analog-to-digital converter and thus optimize the sensitivity of the sensor. In other words, such a control makes it possible to use an optimal reference voltage allowing an improvement. sensor performance in terms of sensitivity. Moreover, the use of a capacitive module of which the microcontroller can dynamically control the load rather than a permanent control of the reference voltage by the microcontroller makes it possible to reduce the current consumption of the sensor. In addition, the use of a resistive module and of a capacitive module makes it possible to reduce the number of components and resources required compared to existing solutions, in particular in a “Vref hopping” type architecture (the principle of which is known. skilled in the art).

[0022] Preferably, the resistive module consists of a single resistance, called an "input" in order to simplify the architecture of the sensor. For example, the value of the input resistance is in the order of 500 ohms.

[0023] More preferably, the capacitive module consists of a single capacitor, called "input", for example of a value of the order of 220 nF in order to simplify the architecture of the sensor.

The capacitive voltage divider can be both CVD type and DCVD type.

[0025] The invention also relates to a motor vehicle comprising at least one sensor as presented above.

Finally, the invention relates to a method for detecting the presence of a user near a sensor as presented above, said method comprising:

- an initialization phase, during which the microcontroller first charges the capacitive module to the supply voltage by connecting the first input-output port to the third input-output port during the charging period, then , once charging is complete, perform a capacitive measurement in order to deduce an optimum reference voltage and the charging time necessary to obtain this optimum reference voltage,

- a reference obtaining phase, during which the microcontroller controls the capacitive voltage divider so that it performs a series of capacitive measurements at the optimum reference voltage determined during the initialization phase in order to obtain a value of reference of the measured capacitive signal, for example a digital value corresponding to the average of the successive capacitive measurements carried out (for example between 4 to 8 acquisitions),

a measurement phase, during which the microcontroller controls the capacitive voltage divider at the determined optimum reference voltage and said capacitive voltage divider periodically measures the voltage value at the terminals of the storage capacitor in order to detect or not a human presence near the sensor. By the terms "capacitive measurements" is meant the measurement of the voltage defined at the terminals of the storage capacity.

According to one aspect of the invention, when the microcontroller detects saturation of the analog-to-digital converter during the measurement phase, then the microcontroller again performs the initialization and reference obtaining phases, in order to modify the optimum reference voltage and the capacitive signal reference, then resumes the measurement phase.

Preferably, the optimum reference voltage is 10 to 20% greater than the voltage measured at the terminals of the storage capacitor in order to avoid saturation of said voltage signal in nominal operation of the sensor, for example in the case where a hand is placed on the handle of an opening with the palm over the entire unlocking zone or else a finger is pressed on a locking zone in the case of a handle sensor.

In one embodiment, the method comprises, between the phase of obtaining the reference and the measurement phase, a determination phase during which the microcontroller determines at least one threshold for detecting a human presence from the capacitive reference signal, the measurement phase then being carried out in order to detect or not a human presence near the sensor as a function of at least one determined detection threshold.

[Description of the drawings]

[0031] Other characteristics and advantages of the invention will become apparent on reading the description which follows. This is purely illustrative and should be read in conjunction with the accompanying drawings in which:

[Fig. 1]: Figure 1 illustrates a first embodiment of the sensor according to the invention, [Fig. 2]: Figure 2 illustrates a second embodiment of the sensor according to the invention, [Fig. 3]: FIG. 3 illustrates an embodiment of the method according to the invention.

[Description of the embodiments]

The sensor according to the invention is intended to be mounted in a motor vehicle and more particularly in a door handle or at the level of a motor vehicle trunk in order to detect the presence of a user, for example to allow unlocking of vehicle doors. FIG. 1 shows an example of an electronic circuit of the sensor 1 according to the invention. The sensor 1 comprises a microcontroller 10 and a capacitive voltage divider 20.

The microcontroller 10 comprises an analog-to-digital converter ADC, a first input-output port E1, a second input-output port E2, a third input-output port E3, a fourth input port -output S1 and a fifth input-output port S2, these last two ports being designated connection input-output ports S1, S2. By the terms "the microcontroller 10 includes an analog-to-digital converter ADC" is meant that the microcontroller 10 implements a hardware analog-to-digital converter ADC or is configured to implement an analog-to-digital converter ADC in a software manner.

The microcontroller 10 is configured to internally electrically connect the first input-output port E1 and the third input-output port E3 so that they are at the same potential and to internally electrically disconnect the first input-output port E1 and the third input-output port E3. The second I / O port E2 is the voltage reference of the ADC analog-to-digital converter. The third input-output port E3 is the power input of the microcontroller 10 at a supply voltage Vcc, in a manner known per se.

In the examples described below, the sensor 1 is of CVD (Differential Capacitive Voltage Divider) type but could just as well be of DCVD (Capacitive Voltage Divider) type in another embodiment.

The capacitive voltage divider 20 comprises a first detection capacitor Ce and a first storage capacitor Cext. Each connector of the first Cext storage capacity is respectively electrically connected to an input-output connection port S1, S2. A resistor R1 is connected between a the fourth input-output port S1 and a terminal of the first detection capacitor Ce connected to the supply voltage Vcc. The first sensing capacity Ce represents the equivalent capacity of the electrode of sensor 1, which varies with the approach to a user's body part, such as a hand. In order to be able to charge the first detection capacitor Ce and to detect a presence in CVD or DCVD mode, the first detection capacitor Ce can be connected intermittently and in a manner known per se (via a switch not shown in the figures) to the voltage power supply Vcc.

The sensor 1 comprises a resistive Rin module connected between the first input-output port E1 and the second input-output port E2 of the microcontroller 10 and a capacitive module Cin, connected between the second input-output port E2 of the microcontroller 10 and a ground M. In this preferred example, the resistive module Rin consists of a single so-called “input” resistor and the capacitive module Cin consists of a single so-called “input” capacity. In another embodiment, the resistive module Rin could include a plurality of resistors and the capacitive module Cin could include a plurality of capacitors.

The microcontroller 10 is configured to internally connect the first input-output port E1 and the third input-output port E3 for a so-called predetermined "charging" period in order to charge the capacitive module Cin and establish thus dynamically the reference voltage of the analog-to-digital converter ADC.

In a second embodiment illustrated in Figure 2, the microcontroller 10 further comprises a sixth input-output port S3 (called "connection" as the fourth input output port S1 and the fifth port d input output S2) and the capacitive voltage divider 20 comprises, in addition to the elements already present in the first embodiment, a first filter capacitor C1, a second storage capacitor Cext2, a second filter capacitor C2, a second resistor R2 and a second detection capacitor Ce2.

The first filtering capacitor C1 is connected between the first input-output port S1 of the microcontroller 10 and the ground M and allows filtering of the current signal flowing between the first input-output port S1 and the first detection capability Ce via the first resistor R1. The first resistor R1 is connected between the first input-output port S1 of the microcontroller 10 and an unlocking terminal designated "UNLOCK" materializing an electrode for unlocking the vehicle doors represented by the first detection capacitor Ce. In other words, the detection of an unlock request by a user is detected when the voltage measured on the UNLOCK unlock terminal exceeds a predetermined threshold.

The second storage capacity Cext2 is connected between the fifth input / output port S2 and the sixth input / output port S3 of the microcontroller 10. The second filtering capacity C2 is connected between the sixth input port -output S3 of microcontroller 10 and ground M and allows filtering of the current signal flowing between the sixth input-output port S3 and the second detection capacitor Ce2 via the second resistor R2. The second resistor R2 is connected between the third input / output port S3 of the microcontroller and a locking terminal designated “LOCK” materializing a locking electrode for the vehicle opening elements represented by the second. detection capacity Ce2, different from the unlocking electrode. In other words, the detection of a lock request by a user is detected when the voltage measured on the LOCK lock terminal exceeds a predetermined threshold.

As a variant, it will be noted that the capacitive voltage divider 20 could, while fulfilling the same function, comprise a number and types of different components and / or arranged differently.

An embodiment of the method according to the invention will now be described with particular reference to Figure 3.

First of all, the microcontroller 10 electrically connects the first input-output port E1 and the third input-output port E3 so that the voltage defined between the first input-output port E1 and the mass M is equal to the supply voltage Vcc of the microcontroller 10, itself defined between the third input-output port E3 and the ground M.

This voltage defined between the first input-output port E1 and the ground M makes it possible to charge the input capacitance of the capacitive module Cin through the input resistance of the resistive module Rin and at the level of the second port d 'input-output E2 which constitutes the reference voltage of the analog-to-digital converter ADC. The electrical connection time between the first input-output port E1 and the third input-output port E3 thus defines the charging time of the input capacitor of the capacitive module Cin. The reference voltage of the analog-to-digital converter ADC can thus be adjusted by the microcontroller 10 by adjusting the charging time t according to the following formula:

[0047] [Math. 2]

Where V _ref-AD c, is the reference voltage of the analog-to-digital converter ADC, Vcc is the supply voltage of the microcontroller 10, "Rin" is the value of the input resistance of the resistive module Rin and "Cin" is the value of the input capacitance of the capacitive module Cin.

At the end of the charging time, the microcontroller 10 electrically disconnects the first input-output port E1 and the third input-output port E3 so that the voltage is fixed and stable across the capacitor input of the capacitive module Cin. The microcontroller 10 then measures the voltage defined between the fourth input-output port S1 and the ground M, that is to say the voltage defined at the terminals of the first capacitor of Cext storage, the variations of which are the image of the variations of the first detection capacity Ce.

Once charged, a capacitive measurement of the voltage at the terminals of the storage capacitor Cext is carried out by the microcontroller 10 using the capacitive voltage divider 20 in order to deduce therefrom an optimum reference voltage, slightly greater than the measured voltage, for example 10%, and the charging time required to obtain this optimum reference voltage.

Then, in a phase of obtaining the reference PH2, the microcontroller 10 controls the capacitive voltage divider 20 so that it performs a series of capacitive measurements at the optimum reference voltage determined during the initialization phase PH1 in order to obtain a reference value of the capacitive signal which will then make it possible to determine the detection thresholds serving as criteria for the detection, in a manner known per se.

Then, in a phase of measurement PH3, the microcontroller 10 controls the capacitive voltage divider 20 so that it periodically measures the value of the voltage defined between the fourth input-output port S1 and the ground M (voltage at the terminals of the first storage capacitor Cext) and compares it with the optimum reference voltage determined during the phase of obtaining the reference PH2 in order to detect or not a human presence, for example of a hand, near the sensor.

If the microcontroller 10 does not detect saturation of the analog-to-digital converter ADC, that is to say that the output value of the analog-to-digital converter ADC is less than (2 ^ADC - ^bits - margin), where ADC_bits is the number of bits of the analog-to-digital converter ADC, then the microcontroller 10 continues to use the optimum reference voltage value defined during the initialization phase PH1.

If the microcontroller 10 detects saturation of the analog-to-digital converter ADC, that is to say that the output value of the analog-to-digital converter ADC is greater than (2 ^ADC - ^bits - margin), then the microcontroller 10 again performs the phases of initialization PH1 and of obtaining the reference PH2 in order to modify the optimum reference voltage and the capacitive signal reference, then phase PH3 is periodically carried out again.

The above example was given for a presence detection in the case of an opening opening with reference both to Figure 1 and Figure 2 (UNLOCK terminal of Figure 2 in particular) but also applies to a detection of presence in the case of an opening locking with reference to both Figure 1 and Figure 2 (LOCK terminal of Figure 2 in particular).

The method according to the invention thus allows the microcontroller 10 to adapt the reference voltage V _re t_ADc of the analog-to-digital converter ADC in order to optimize the use of the sensor 1 and thus to improve its nominal performance.

In an architecture of the "Vref hopping" type, the invention makes it possible in particular to reduce the type of components by allowing control of the reference voltage from the load of the capacitive module Cin in order to define the stages of "Vref hopping ”, in a manner known to those skilled in the art.

[0059] References

1: sensor

10: microcontroller

20: capacitive voltage divider

ADC: analog-to-digital converter

E1: first input-output port

E2: second input-output port

E3: third input-output port

51: fourth input-output port (called "connection")

52: fifth input-output port (called "connection")

Vcc: supply voltage

Ce: first detection capability

Cext: first storage capacity

R1: resistance

M: mass

Rin: resistive module

Cin: capacitive module

53: sixth input-output port (called "connection")

C1: first filtering capacity

Cext2: second storage capacity

C2: second filtering capacity

R2: second resistance

Ce2: second detection capacity

U N LOCK: unlocking terminal

LOCK: locking terminal

Claims

[Claim 1] Presence detection sensor (1) for unlocking a motor vehicle opening, said sensor (1) comprising:

- a microcontroller (10) comprising an analog-to-digital converter (ADC), a first input-output port (E1), a second input-output port (E2), constituting the voltage reference of said analog-to-digital converter (ADC), a third input-output port (E3), voltage supply (Vcc) of the microcontroller (10), a fourth input-output port (S1) and a fifth input-output port (S2), known as “connection”,

- a capacitive voltage divider (20), connected to said connection input-output ports (S1, S2) and comprising at least one detection capacitor (Ce, Ce2) and at least one storage capacitor (Cext, Cext2) ,

the sensor (1) being characterized in that it comprises a resistive module (Rin) connected between the first input-output port (E1) and the second input-output port (E2) of the microcontroller (10) and a capacitive module (Cin), connected between the second input-output port (E2) of the microcontroller (10) and a ground (M), and in that the microcontroller (10) is configured to internally connect the first input-output port (E1) and the third input-output port (E3) for a predetermined so-called “charging” time of the capacitive module (Cin) in order to dynamically establish the reference voltage of the analog-to-digital converter (ADC).

[Claim 2] A sensor (1) according to claim 1, wherein the resistive modulus (Rin) consists of a single resistor.

[Claim 3] A sensor (1) according to the preceding claim, wherein the value of the resistance is of the order of 500 W.

[Claim 4] A sensor (1) according to any preceding claim, wherein the capacitive module (Cin) consists of a single capacitor.

[Claim 5] A sensor (1) according to the preceding claim, wherein the value of the capacitance is of the order of 220 nF.

[Claim 6] A sensor (1) according to any preceding claim, in which the capacitive voltage divider (20) is of the CVD or DCVD type.

[Claim 7] A motor vehicle comprising at least one sensor (1) according to any one of the preceding claims.

[Claim 8] A method of detecting the presence of a user near a sensor (1) according to any one of claims 1 to 6, said method comprising:

- an initialization phase (PH1), during which the microcontroller (10) first charges the capacitive module (Cin) to the supply voltage (Vcc) by connecting the first input-output port (E1) to the third input-output port (E3) during the charging time, then, once the charging is complete, perform a capacitive measurement in order to deduce an optimal reference voltage and the charging time necessary to obtain this voltage of optimal reference,

- a phase of obtaining the reference (PH2), during which the microcontroller (10) controls the capacitive voltage divider (20) so that it performs a series of capacitive measurements at the optimum reference voltage determined during phase d 'initialization (PH1) in order to obtain a reference value of the measured capacitive signal,

- a measurement phase (PH3), during which the microcontroller (10) controls the capacitive voltage divider (20) to the determined optimum reference voltage and said capacitive voltage divider (20) periodically measures the voltage value at the terminals of the storage capacity (Cext, Cext2) in order to detect or not a human presence near the sensor.

[Claim 9] A method according to the preceding claim, wherein when the microcontroller (10) detects saturation of the analog-to-digital converter (ADC) during the measurement phase (PH3), then the microcontroller (10) again performs the phases. initialization (PH1) and reference obtaining (PH2), in order to modify the optimum reference voltage and the capacitive signal reference, then resumes the measurement phase (PH3).

[Claim 10] A method according to any one of claims 8 or 9, wherein the optimum reference voltage is 10 to 20% greater than the voltage measured at the terminals of the storage capacitor (Cext, Cext2).